1. Field of the Invention
The subject matter of this invention is related generally to solid state devices for detecting phase imbalance in a three-phase load and is related specifically to a DC ripple detecting device for accomplishing this purpose.
2. Description of the Prior Art
It is known in the prior art to provide phase imbalance logic circuits which may be utilized to trip a circuit breaker to protect a three-phase load, such as a motor if one of the phases completely drops out. It would be advantageous if means were provided for sensing current imbalance in one or more phases in a three-phase load where the current imbalance is not necessarily complete, that is, where the current does not necessarily completely go to zero, but rather is maintained at some intermediate value between zero and the balanced value or even at some higher value than the balanced value. In addition, it would be advantageous of a DC ripple detecting device could be provided which somehow referenced the ripple voltage against voltage peak rather than zero. This would give greater sensitivity in the ripple measuring operation. Furthermore, it would be in keeping with the concept that ripple is generally measured as some percent of full scale, or rated voltage.